The present invention relates to a method and an apparatus for plasma processing for a semiconductor device, and more particularly to a method and an apparatus for plasma processing in which plasma is pulse-modulated to increase the precision of plasma processing.
As semiconductor devices are miniaturized to smaller and smaller sizes, three-dimensional structure transistors, called Fin Field Effect Transistors (hereinafter called Fin-FET), are mass-produced today on a commercial basis. To respond to the mass production of three-dimensional structure transistors, the dry etching technology, a key to micro-fabrication, requires higher-level micro-fabrication, higher-aspect-ratio, and higher-precision etching for a complex profile not found in the conventional two-dimensional transistors. To meet this need, a breakthrough technology is required.
A processing profile, such as an aspect ratio, changes over time during etching, and each profile has the optimal etching condition. However, in many conventional etching methods, the condition is not changed according to a change in the profile.
One of the conventional technologies for changing conditions during etching is disclosed, for example, in JP-A-2009-239054. The disclosed method for manufacturing a silicon structure includes a first electric power application process wherein, in a process for etching a silicon substrate by using plasma generated by alternately introducing an etching gas and an organic sediment producing gas, applied power to a substrate when introducing the etching gas is kept constant during a predetermined time from the start of the etching, and a second electric power application process, wherein the applied power to the substrate at the introducing of the etching gas is increased with time, after the predetermined time has elapsed.
JP-A-2-312227 discloses a technology for dividing the etching period of a sample 11 into two. In the first half (several tens of seconds), high electron-temperature etching (mode 1) is performed using pulse discharge.
In the second half (several seconds to 20 seconds), usual low-damage etching (mode 2) is performed.